Windows 10 displays the touch keyboard automatically whenever you need to input text while using a touchscreen display. You can also activate the keyboard manually from the keyboard icon in the taskbar (right-click the taskbar and check the "Show touch keyboard button" option if you can't see it).
By default, the touch keyboard provides a simplified typing layout aimed at tablet users. This has large keys but a minimal set of commands and modifiers. Although you can use Ctrl, other important keys like Alt, Tab and F1-F12 are missing.
You can customise the keyboard to display a complete layout that's reminiscent of a hardware keyboard. Tap a text field or the taskbar keyboard button to bring up the touch keyboard. Press the keyboard settings icon in the top-left of the keyboard. Next, tap the keyboard option that is second from the right to enable the standard layout.
The keyboard will switch to a regular PC-style layout with a function key row and Ctrl, Alt and Tab keys. You can switch back by tapping the keyboard settings icon in the top-left and this time choosing the left-most keyboard layout. The other two options enable compact floating and split mode respectively, with the final button activating handwriting input.